Short time to positivity in blood culture with clustered gram-positive cocci on direct smear examination is highly predictive of Staphylococcus aureus.

are not usually considered clinically significant unless 2 or more cultures are positive, whereas presence of Staphylococcus aureus in only 1 blood culture bottle is usually sufficient to diagnose a true bacteremia. Initiation of antibiotic treatment on the sole presence of gram-positive cocci on smear examination is not recommended because it is costly and increases unnecessarily antibiotic use and selective pressure. By contrast, delay in treating S aureus bacteremia may be deleterious for the patient. Therefore, rapid differentiation between S aureus and CNS in blood cultures can help to make the correct medical decision. Because traditional isolation and identification of staphylococci require 18 to 24 hours, several rapid methods have been assessed to speed up the differentiation between S aureus and CNS in blood cultures bottles with clustered gram-positive cocci on direct smear examination. These methods include API RAPIDEC staph